Plural electron gun assembly

ABSTRACT

An electron gun for a color cathode-ray tube includes three sets of axially aligned cylindrical grids supported upon glass side rods by radially projecting studs of different widths. In fabrication of the gun, and during a beading operation in which the side rods are in molten state, each of the side rods is supported in a beading trough including notched wall sections in the regions of insertion of the relatively wider ones of the studs into the rods. The notched sections accommodate formation of strain-relieving bulges in the regions of wider stud insertion in the molten rods.

Unite atet [72] Inventors Bruce G.Marlrs [54] PLURAL ELECTRON GUNASSEMELY 3 @laims, 6 Drawing lFigs.

[52] US. Cl 313/70 (3, 313/251 [51] Int. Cl ..llll0lj 25/50, HOlj 29/02,HOlj 1/92 [50] Field of Search 313/69 C,

Primary Examiner-Robert Segal AttorneyCarl ll. SynnestvedtAdS'llltAC'll: An electron gun for a color cathode-ray tube includesthree sets of axially aligned cylindrical grids supported upon glassside rods by radially projecting studs of different widths. infabrication of the gun, and during a heading operation in which the siderods are in molten state, each of the side rods is supported in aheading trough including notched wall sections in the regions ofinsertion of the relatively wider ones of the studs into the rods. Thenotched sections accommodate formation of strain-relieving bulges in theregions of wider stud insertion in the molten rods.

PLURAL ELECTRON GUN ASSEMBLY BACKGROUND OF THE INVENTION This inventionrelates to electron guns and, while of broader applicability, isdirected especially to improvements in structure and fabrication ofelectron guns for color cathode ray tubes.

In guns of the aforementioned type, individual gun grids are supportedin the desired axial and radial disposition relative to one another bymeans of mounting studs embedded in insulative material, such aselongate glass rods or beads. In conventional practice, the studs areembedded in the glass rods while in a heat-softened state, and while thegrids and rods are held by suitable fixtures or the like. Afterassembly, the gun structure is held in place by a conventionalinsulative tube base provided with pins that serve as terminals for theseveral grids of the gun. In the manufacture of one such structure knownas an einzel gun, there are five such grids, one of which is a focusgrid known as grid 4, or G4, and which particularly is susceptible toundesirable arching due to the relatively high potential to which it issubjected. It has been found advantageous to form this grid as a singlestamping comprising a cylindrical body portion with rolled edges andradially presented flat spades serving as the studs. Prior to thisinvention these spades have presented problems since, at the G-4location, they extend transversely of, rather than parallel to, the longaxis of the glass rods, with a resulting tendency to chip or extendbeyond the glass and expose a sharp corner of the spade. This rendersthe assembly highly susceptible to arcing between grid 4 and adjacentelements. Also, there is a tendency to chipping of the rod in thevicinity of the cathode where there may be as many as four stud elementsextending side by side into the rod.

It is an objective of the present invention to provide an improvedelectron gun structure, and method of fabricating the same, thatovercomes the aforementioned difficulties.

SUMMARY OF THE INVENTION In achievement of the foregoing, as well asother general objective, the present invention is featured by a novelelectron gun structure, and method of fabrication thereof, characterizedby provision of means for relieving the glass beading strains whichpreviously were encountered in the manufacture of such structure whenthe grid mounting studs were inserted into the heat-softened glassbeads, or rods. Relief is achieved by removal of opposed sections of thesidewalls of the glass beading trough, so that during the beadingoperation softened glass in the vicinity of the studs is allowed to flowfreely as the studs are urged into the glass. Upon cooling, the glasshardens to form strain-free bulges about the outer edges of the studs.Advantageously, provision of the stain-free bulges greatly improvesreliability of the gun.

The manner in which the foregoing as well as other objectives of theinvention may best be achieved will be understood more clearly from aconsideration of the following description, taken in light of theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational showing,partly in section and with parts broken away, showing one set of axiallyaligned cylindrical grids of an einzel cathode ray tube gun structureembodying the invention;

FIG. 2 is an enlarged sectional view of apparatus illustrated in FIG. 1,but illustrating the three sets of grids characteristic of such a gun,the view being taken generally in the direction of arrows 2-2 applied toFIG. 1;

FIG. 3 is a sectional view of a portion of the apparatus shown in FIG.1, as seen looking generally in the direction of arrows 3-3 appliedthereto; and

FIGS. 4, 5, and 6 are perspective views including portions of the gunstructure illustrated in FIGS. 1 and 2, and showing techniques utilizedin assembling the same.

DESCRIPTION OF THE PREFERRED EMBODIMENT With more particular referenceto the drawing, and first to FIG. 1, an electron gun assembly 10 madeaccording to the invention is mounted in the neck 11 of a color cathoderay tube 12. Portions of the net 11 are shown broken away forconvenience of illustration. Gun assembly 10 includes three individualguns, each comprising tubular and cup-shaped, axially aligned grids 15,16, 17, 18 and 19 on support rods 23 mounted on certain of the theterminal pins 13. The electrodes, or grids, of the interiorly disposedgun assembly are electrically connected by conventional strap connectors(not shown) to appropriate ones of terminal pins 13 extending throughthe base portion 14 of the tube neck 11. Gun grids 15 to 19 cooperatewith one another, and with a conventional heater and cathode therefor(not shown), and several conventional external voltage sources ofdifferent values, to produce a high velocity stream of electrons. Suchoperation is conventional, and need not be discussed in further detailfor an understanding of the invention.

Considering gun assembly 10 in more detail, and with reference also toFIGS. 2 and 3, three identical guns, one for each color, are spaced atsubstantially equal radial distances about the axis of tube neck 11. Theabove-identified grids of each gun are further characterized as controlgrid 15, accelerating grid 16, and focus grids 17, I8, and 19. The focusgrids 19 support a conventional convergence shield 21 electricallyconnected, by the usual spring snubbers (not shown), to the insideconductive coating of the tube. Pins 13 support the cathode and heaterelements (not shown) within the control grid 15.

Each of grids 15, 16, 17 and 19 includes a pair of mounting studs 22extending generally tangentially therefrom, at an inclined angle. ofabout Studs 22 of adjacent corresponding grids face one another, as isthe usual practice, so that a pair extend into a corresponding supportrod 23 substantially in line with the long axis of the rod and wellspaced inwardly from the sides of the rod.

I-Iowever, and as is best seen in FIG. 2, the construction of each ofthe focus grids 18, also known as the G-4 grids, is such that its studs24, unlike the other studs, extend transversely of the axis of extensionof a glass rod 23. Adjacent pairs of studs 24, see for example the pairshown at 24a and 24b in FIG. 2, span almost the full width of the rod.Preferably, each of grids l8 and their studs 24 are formed as a unitary,integral subassembly from a metal stamping. This construction affordsadvantages over prior art electrode constructions in which G-4 grid, orthe like, is formed with its rolled edges, and its mounting studs arespot welded to the grid. In contrast, the studs 24 and grid 18 comprisea single piece stamping, which construction has a reduced fabricationcost and lends itself to reducing the axial dimension of the grid and toimprove edge rolling, since provision of extra material for welding ofthe stud is not required.

In further, and more especial accordance with the invention, thesubstantial lateral extension of the G-4 grid studs 24 is accommodatedby lateral bulges 25 in corresponding regions of a rod 23. These bulgesprevent chipping of the glass or exposure of sharp edges of the grid.The bulges are shown in section and in full in FIG. 2. The procedure bywhich bulges 25 are formed, in conjunction with apparatus shown in FIGS.4, 5, and 6, will be described in what follows.

There is shown in FIG. 4 a partial gun assembly, together with a beadingtrough 26 within which a corresponding glass rod 23 is nested. Inachievement of the particular orientation illustrated, sets of electrodecomprising the three guns are held in their desired positions bysuitable fixture apparatus (not shown), of a type well known in the art.Preferably, the fixture holds the electrodes in such a position thattheir axes extend generally vertically, with corresponding verticalalignment of sets of mounting studs 22 and 24. The beading troughs 26,of which there are three, are held in vertical position opposite a likenumber of sets of aligned mounting studs. As is known, the troughs 26further are mounted for reciprocable frontal movements toward and awayfrom the set of studs, as is indicated by directional arrows applied toFIGS. and 6. Each of the troughs is generally channel shaped, and is sodimensioned as to retain a glass rod 23 of generally rectangular crosssection. In accordance with conventional practice, means 28 (FIG. 4) isprovided to play a flame onto each rod in each region of stud mounting.Upon attainment of the desired heatsoftened consistency of such rodregions, the troughs are moved toward the studs a sufficient distance toembed the latter (FIG. 5), and then retracted to allow the rods to cool(FIG. 6).

In especial accordance with the invention, the low-profile" leg portionsof the conventional channel-shaped troughs 26 are provided with notchedsections 29 in the regions of stud insertion, so that insertion of studs24 into the heat-softened rods 23 urges sides of the rods outwardly intothe notched sections to form strain-relief bulges 25. These areparticularly important in the region of said studs 24, since theycomprise sheets lying in a plane transverse the axis of the glass rods.

While not illustrated, leg portions of channel-shaped troughs 26 abo arecut away in the regions of extension of both the studs 27 of the cathodeheater supports 20, and the studs of the several terminal and gunsupport brackets designated generally by the numeral 30 (FIGS. 1 and 3).Relieving of the glass rods in these regions permits bulging, as isillustrated in FIG. 3, to accommodate insertion of the larger number ofmounting studs 27. For example, the left hand rod 23 in FIG. 3 supportsfour such mounting studs with ease, in accordance with teachings of theinvention.

Comparative tests between identical gun assemblies made according to theinvention and those not made according to the invention have evidencedremarkable reduction in arcing at the G-4 location. In short, theinvention has overcome a serious problem encountered in the fabricationand use of color cathode-ray tube electron guns.

We claim:

1. In an electron gun assembly of the type comprising three similargroup of coaxial, generally tubular electrodes symmetrically spaced fromeach other on longitudinally converging axes for forming three distinctconverging electron beams, the combinations comprising: support meansincluding a pair of support studs for each electrode, the support studsfor each group of electrodes being formed to lie adjacent correspondingsupport studs of the other groups; three elongate glass rods ofgenerally rectilinear cross section engaging said support studs andrigidly supporting the same, the support studs of at least one pair ofcorresponding electrodes present in two adjacent electrode groups beingin adjacency and having portions extending transversely of and imbeddedin a corresponding one of said rods, said studs further including outeredge portions extending with angularity to said rods and intersectingcomer edge portions thereof thereby spanning substantially the fullwidth of said one rod, said rod including laterally bulged regionsformed by heat softening of the rod and disposed at each of the regionsof intersection of said lastrecited support studs with said comer edgeportion, said bulged regions preventing cracking of the glass of therod, or protrusion of said imbedded stud portion laterally of said rod.

2. A gun assembly according to claim 1, and further characterized inthat said studs are fonned laterally with corresponding ones of said onepair of electrodes.

3. A gun assembly according to claim 2, and further characterized inthat said studs are generally flat and include angle sections extendingalong confronting edge portions of the recited adjacent studs.

mg? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,93 Dated September 28, 1971 Inventcfls) Bruce G. Marks et al.

It is certified that error appears in the above-identified patent? andthat said Letters Patent: are hereby corrected as shown below:

Column 1, line 21, "arching" should read arcing Column 2, line 6, "net"should read neck Column L, line 6, "group" should read groups 3 line 9,"combinations" should read combination and line 28, "laterally" shouldread integrally Signed and sealed this 21st day of March 1972.

(SEAL) Attestz EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents

1. In an electron gun assembly of the type comprising three similargroups of coaxial, generally tubular electrodes symmetrically spacedfrom each other on longitudinally converging axes for forming threedistinct converging electron beams, the combination comprising: supportmeans including a pair of support studs for each electrode, the supportstuds for each group of electrodes being formed to lie adjacentcorresponding support studs of the other groups; three elongate glassrods of generally rectilInear cross section engaging said support studsand rigidly supporting the same, the support studs of at least one pairof corresponding electrodes present in two adjacent electrode groupsbeing in adjacency and having portions extending transversely of andimbedded in a corresponding one of said rods, said studs furtherincluding outer edge portions extending with angularity to said rods andintersecting corner edge portions thereof thereby spanning substantiallythe full width of said one rod, said rod including laterally bulgedregions formed by heat softening of the rod and disposed at each of theregions of intersection of said last-recited support studs with saidcorner edge portion, said bulged regions preventing cracking of theglass of the rod, or protrusion of said imbedded stud portion laterallyof said rod.
 2. A gun assembly according to claim 1, and furthercharacterized in that said studs are formed integrally withcorresponding ones of said one pair of electrodes.
 3. A gun assemblyaccording to claim 2, and further characterized in that said studs aregenerally flat and include angle sections extending along confrontingedge portions of the recited adjacent studs.